Richard Kay, left, with David Wynne-Morgan, says the late Princess Diana would love to see William as a father. / Dave M. Benett, Getty Images

by Kim Hjelmgaard, USA TODAY

by Kim Hjelmgaard, USA TODAY

How would the late Princess Diana have felt about the birth of her first grandchild?

Richard Kay, a friend of Diana's and a Daily Mail columnist, says she'd be thrilled with the arrival, but that adding the title "grandma" to her résumé might make her feel old.

"She would obviously be absolutely thrilled at the prospect of having a new baby in the palace," Kay said Monday. "I'm not sure how thrilled she would have been at becoming a grandmother, though. That would have made her feel old. Diana would have been 52 now. Time marches on."

Kay says Diana would have really loved the thought of a female royal heir. "I think she would love William to have a daughter above all," Kay says. "She longed to have a daughter and never did."

Diana died in 1997 in a car accident. Prince William was 15 at the time.